WO2003045643A2

WO2003045643A2 - Laminated guide bar

Info

Publication number: WO2003045643A2
Application number: PCT/SE2002/002166
Authority: WO
Inventors: Roger Hermansson; John Flaten; Lennart Ekrud; Terje Berget
Original assignee: Aktiebolaget Electrolux
Priority date: 2001-11-26
Filing date: 2002-11-26
Publication date: 2003-06-05
Also published as: AU2002353733A1; AU2002353733A8; WO2003045643A3; SE0103947L

Abstract

A guide bar (10) for a chain saw. The guide bar comprises two flat side plates (11, 13) and a flat intermediate layer (12). The intermediate layer (12) is made of a material with lower density than the material in the side plates (11, 13) and is smaller than the side plates so that a guide groove (14) for a saw chain is defined around the periphery of the guide bar (10). The side plates (11, 13) and the intermediate layer (12) are bounded together by an adhesive material that creates a stiff bound between the side plates (11, 13) and the intermediate layer (12) so that the side plates (11, 13) and the intermediate layer (12) constitutes a sandwich-construction.

Description

Laminated Guide bar

The claimed invention relates to a guide bar for a chain saw. The guide bar comprises two flat side layers and a flat intermediate layer made of a material with lower density than the material in the side layers. The intermediate layer is smaller than the side layers so that a groove for a saw chain is created around the periphery of the guide bar

Chain saws and other hand held tools have been under a high level of development during the last years. Great efforts have been done to improve the performance and the ergonomic features for the tools.

New material and methods for manufacturing the different components have made it possible to reduce the weight of the tools as well as make the tools stronger. The tools are also more reliable. All these achievements improve the working conditions for the operator. Great progress has been done with the machinery and casing while the development of the guide bar has been struggling with several problems. The problem is that all solutions for reducing the weight of the guide bar has ended in that the performance of the guide bar is deteriorated because of a reduced torsional and / or bending stiffness.

Guide bars normally comprises three different layers. Layer one and three constitutes the outside of the guide bar and are normally made of the same type of material. The material is usually some kind of steel. Between layer one and three is layer two placed as an intermediate layer. This layer could be made of another material than layer one and three. The intermediate layer has a smaller length and width than layer one and three that are identically shaped so that a groove is defined between layer one and three. The groove extends around almost the entire edge of the guide bar. The saw chain is sliding in this groove. Different types of saw chains require grooves with different depth and width so the size of the groove is selected to meet the requirements of the saw chain in use. The width of the groove is changed by the thickness of the intermediate layer and the depth of the groove is related to the length and with of the intermediate layer.

The three layers are attached to each other by welding. Normally is spot welding or pressure welding used. In order to make sure that the welding achieves enough strength and that no welding spark end up in the groove for the saw chain is the centre of the welding spot placed about 6 millimetres inside the edge of the intermediate layer, which is the same as the bottom surface of the groove. The distance from the centre of the welding spot to the edges of the groove is consequently 6 millimetres plus the depth of the groove. This distance makes the sides of the groove bend outwards when the saw chain is exposed to high load during use. The movements in the sides of the groove generate a play in the groove that allow sideways movements of the saw chain. These movements in the saw chain have a negative influence on the performance of the chain saw and will also increase the wear on the guide bar and the saw chain.

The weight of the guide bar is an important parameter in order to facilitate and increase the efficiency of the work for the operator. Several different types of guide bars have been developed where the intermediate layer has holes to reduce the weight of the tool. A guide bar of this type is described in the patent document DE4219956A1. These guide bars have a lower weight but the torsional and bending stiffness are reduced, which is bad for the performance of the guide bar.

Another alternative in order to reduce the weight of the guide bar is use an intermediate layer in a material with low density like for example aluminium or a plastic material. These types of guide bars are described in patent document US4693007A. An intermediate layer in aluminium or a plastic material reduces the weight of the guide bar but the manufacturing of the guide bar get more complicated since the material in the intermediate layer not is suitable for welding. To solve this problem is the intermediate layer provided with recesses of a material suitable for welding. The recesses are placed so that they are positioned where the welding spots are expected to be. This type of guide bars is expensive to manufacture.

All the described types of guide bars are complicated, which means that they are expensive to manufacture. The guide bars also have the drawback that the holes and the use of lighter materials to reduce the weight of the guide bar reduces the torsional and bending stiffness of the guide bar, which makes these solutions not satisfying.

There are also guide bars with recesses of a lighter material like aluminium or plastic in the outer layers, see for example US4837934A. This solution is also complicated and therefore expensive to manufacture. The result is also for this guide bar that the torsional and bending stiffness are reduced. This solution is therefore not a good alternative to get a lighter guide bar.

All solutions to reduce the weight of the guide bar has ended in a more complicated process for manufacturing which makes the guide bars expensive without improving the performance of the guide bar.

An invention according to the characterising portion of claim 1 solves the problems described above. The new features of the claimed invention that the flat side layers and the flat intermediate layer are bounded together by an adhesive material. The adhesive creates a stiff bound between the side layers and the intermediate layer. The side layers and the intermediate layer constitutes a sandwich-construction.

The claimed guide bar comprises three layers. Layer one and three is the outer sides of the guide bar and between layer one and three is an intermediate layer made of a material with lower density than the material in layer one and three to reduce the weight of the guide bar. The layers are bounded together by an adhesive material that is cured during exposure to heat and pressure to achieve maximum strength in the bounding.

If an adhesive material bound the layers is it possible to use an intermediate layer made of a material that not has to be suitable for welding. This makes it possible to use a light material like for example aluminium or a plastic material.

The bounding is made so that the adhesive is acting on the entire surfaces of the layers that are in contact with each other. The three layers thus constitute a sandwich laminate where the intermediate layer is the core between the outer layers. This type of guide bars therefore has a higher torsional and bending stiffness than conventional guide bars. This type of guide bar also has a considerably lower weight than the existing guide bars with the same stiffness.

The adhesive material is applied in such an amount that it covers as much as possible of the surfaces that will be bounded together to get the maximum strength out of the bounding. This means that the layers are bounded together all the way out to the edges of the intermediate layer, which is the same as the bottom of the groove that is extending around the periphery of the guide bar. The free length of the sides is therefore shortened with the same distance that the welding spot is placed from the edge of the intermediate layer, which is about 6 millimetres. When the chain saw is in use and the saw chain exposed to high loads will the shorter distance reduce the outward bending of the sides of the groove. The sides of the groove are thereby more stable and gives better support for the saw chain. This improves the performance of the chain saw and reduces the wear on the groove as well as the saw chain.

A guide bar of the claimed type will have less remaining deformations after exposure to high loads than a conventional guide bar because of its high strength and stiffness. This means that the claimed type of guide bar suffers a lower risk to get permanent deformations than a conventional guide bar when exposed to high loads.

The claimed guide bar is also easy to manufacture since there is no need for holes or recesses of other materials in the intermediate layer to enable the layers to be secured to each other. This makes the production efficient and fast.

The higher torsional and bending stiffness increases the resonance frequency for the guide bar compared to conventional guide bars. This is an advantage since the amount of vibrations generated in the guide bar is reduced. A reduction in the amount of generated vibrations in the guide bar also reduces the amount of vibrations that are transmitted to the operator. This improves the working conditions for the operator.

The claimed guide bar is also more reliably and safer for the operator since the big surfaces that the adhesive is acting on to keep the layers bounded together increases the bounding strength compared to layers fastened to each other by welding. This reduces the risk for separation or tearing of the layers in the guide bar during use.

The use of adhesive materials for bounding of different materials makes it necessary to use an adhesive and a method for manufacturing of the guide bar that will ensure a reliable bounding between the layers. The bounding must also have enough strength to meet the requirements of the guide bar. The claimed guide bar comprises three layers. The first and the third layer are the outer sides of the guide bar and are made of steel. The material in the intermediate layer does not affect the stiffness of the guide bar as much as the material in the outer layers and is therefore made of a lighter material, for example aluminium or a plastic material, in order to reduce the weight of the guide bar. The three layers are substantially flat and the surfaces of the layers substantially even to provide a large surface for the adhesive to act on.

The adhesive that is used to bind the three layers must provide a strong bounding even though the layers are made of different material. The combinations of material that are most likely are steel - aluminium, steel - plastic material or if a very stiff guide bar is required steel - steel.

Adhesives that are usable for this application are for example epoxy-glues, acrylic- glues, metacrylic-glues or polyurethane-glues. All the different types of glue provide a strong and stiff bounding between the layers. These types of adhesive also make the manufacturing easy.

Before the adhesive is applied on the surfaces are the surfaces cleaned accurately to guarantee a god adhering between the adhesive and the surface of the layer. The adhesive is then applied in strings on the surface according to a predetermined pattern.

The pattern is developed and calculated to make sure that adhesive is spread over the entire surface of the layer when the layers are pressed together. When all three layers are placed in the right position in relation to each other is the guide bar heated to the critical temperature where the adhesive starts curing. The adhesive is then cured at a constant temperature and under pressure until the bounding has achieved maximum strength.

In order to strengthen the groove is the sides of the groove, the bar rails, annealed. That means that the bar rails are heated to a specific temperature for the steel that the bar rails are made of. At this specific temperature starts the structure of steel to change so that the material gets harder. The annealing also reduces the amount of tensions from earlier tooling of the material in the layers. The annealing of the bar rails is preferably co- ordinated with the heating of the guide bar to cure the adhesive. This co-ordination simplifies the manufacturing process since one moment is eliminated.

There is a risk that layers bounded by an adhesive material that is cured under a high temperature and pressure will slip in relation to each other during manufacturing before the adhesive is cured. This problem is solved by applying small amounts of a quick- acting adhesive between the surfaces so that the layers are secured to each other and prevented from slipping during the curing of the adhesive. The adhesive material is applied in the predetermined pattern on the surface of the layer before the quick-acting adhesive finally is applied at some small areas on the surface of the layer. The layers are then put together and held in the right position in relation to each other by the quick- acting adhesive until the adhesive is cured at high temperature and pressure so that the bounding achieves the maximum strength.

One embodiment of the claimed invention is illustrated in the drawing.

Figure 1. Illustrates a cross section of a laminated guide bar with layers bounded by an adhesive material.

A guide bar 10 comprises three different layers 1 1, 12 and 13. The first layer 11 and the third layer 13 have identical shape while the second intermediate layer 12 has a smaller area since the intermediate layer 12 is shorter and has less width that the first and third layer 11 and 13. All three layers 11, 12 and 13 are made of substantially flat sections with constant thickness.

When the three layers 1 1, 12 and 13 are put together is a groove 14 defined around the edge of the guide bar 10 because of the smaller intermediate layer 12. The groove 14 is intended for a not illustrated saw chain that slide in the groove 14. The width of the groove 14 is related to the thickness of the intermediate layer 12 and the depth of the groove 12 to the size of the intermediate layer 12. Different saw chains requires different groove width so the thickness and the size of the intermediate layer 12 are selected so that the guide bar 10 will fit the selected type of saw chain. The three layers 1 1, 12 and 13 are bounded by two layers of adhesive material, a first layer 15 and a second layer 16 that is acting on almost the entire surfaces of the layers that are in contact with each other. The thickness of the adhesive layers 15 and 16 are preferably as constant as possible so that the width of the groove not is changing around the guide bar 10. The thickness of the adhesive layers are between 0,02 - 0,20 mm and preferably between 0,05 - 0,10 mm to ensure maximum strength in the bounding.

The outer layers, layer 1 1 and 13, are made of steel to make sure that the guide bar 10 gets a high torsional and bending stiffness. Steel is also resistant to wear. The intermediate layer 12 on the other hand is not exposed to the same loads and wear and is therefore made of a material with lower density to reduce the weight of the guide bar 10. Suitable materials for the intermediate layer 12 are aluminium or a plastic material.

The outer edge of the sides of the groove 14 is called a bar rail 17 and is exposed to a lot of wear from the saw chain during use of the chain saw. In order to increase the resistance of the bar rails 17 are they annealed. Annealing means that the material is heated to a temperature that is specific for the selected material. When the temperature of the material reaches the specific temperature does the material starts to harden. This process is preferable co-ordinated with the heating of the guide bar to cure the first and second layers of adhesive material 15 and 16. This co-ordination reduces the numbers of steps in the manufacturing of the guide bar which simplifies the production of the guide bar 10.

Claims

1. A guide bar (10) for a chain saw, said guide bar comprising: two substantially flat side layers (11, 13), a substantially flat intermediate layer (12) made of a material with lower density than the material in the side plates

(11, 13), said intermediate layer (12) being smaller than the side plates so that a guide groove (14) for a saw chain is defined around the major part of the periphery of the guide bar (10), characterised in that the side layers (1 1, 13) and the intermediate layer (12) are bound together by an adhesive material that creates a stiff bound between the side layers (11, 13) and the intermediate layer

(12) so that the side layers (1 1, 13) and the intermediate layer (12) constitutes a sandwich-construction.

2. A guide bar according to claim 1, characterised in that the three layers (11, 12 and 13) are bound by two layers of adhesive material, a first layer (15) and a second layer (16) that is acting on almost the entire surfaces of the layers that are in contact with each other

3. A guide bar according to claim 1 or 2, characterised in that the intermediate layer (12) is made of aluminium or a plastic material.

4. A guide bar according to claim 1, 2 or 3, characterised in that the side plates (11, 13) is made of a metal, preferably steel.

5. A guide bar according to claim 1, 2, 3 or 4, characterised in that the adhesive is an epoxy-glue, an acrylic-glue, a metacrylic-glue or a polyurethane-glue.

6. A guide bar according to claim 2, characterised in that the thickness of the adhesive layers (15, 16) are between 0,02 - 0,20 mm.

A guide bar according to claim 2 or 6, characterised in that the thickness of the adhesive layers (15, 16) preferably are 0,05 - 0,10 mm for maximum strength of the connection.

8. Method for manufacturing a guide bar (10) according to any of claim 1-7 comprising the steps;

Clean the surfaces of the layers that will be bound to each other,

Applying adhesive on one of the surfaces that will be in contact wit each other according to a predetermined pattern that will ensure that adhesive is spread over the entire surface when the layers are put together,

Curing of the adhesive by heating the layers (11, 12, 13) and the adhesive to a specific temperature for the adhesive where the adhesive starts curing while pressing on the outer surfaces of the guide bar (10) until the adhesive is cured.

9. Method according to claim 6, characterised in that the sides of the groove (14) is annealed at the same time as the guide bar (10) is heated to cure the adhesive.

10. Method according to claim 6 or 7, characterised in that the side layers (11, 13) and the intermediate layer (12) are held in the right position in relation to each other by a quick-acting adhesive until the adhesive material is cured.